Electrode



June 28, 1938. B. O'BRIEN 2,121,882

ELECTRODE I Filed April 18, 1934 3 Sheets-Sheet 3 I I I I I ITI I I l II I I ITI 'I I IIIIIITIIIIIIIIITIIIIlIIIITIIIIIIIIIUIIIlIIIITIIIIIIIImmlIIIMIIIIIIIHIIIIIIIIEIIIIIIWIIIIIIIII'fiIIIIlIIffiIIIIIIIBIIIIIIIiiII I I I T: I I l I I I!I'I'IIIIIIIII'I'IIIIIIIIITIIIIIIIIITIIIIIIIIITIIIIIIIITIIIIIIIII'fiIIIIIIIIfiIIIIIIIflIIIIIIIIIfIIIIIIIIIIIIIIIIIIFIIIIIIIIIFIIIIIIIM l I I l I ITI l I I I I l ITI I IIIIIII'I'IIIIIIIIITIIIIIIIIITIIIIIIIIITIIIIlIIII'fiIIIIIIImIIIIIIImIIIIIIIiTIIIIWIIIIIIIIIIIIIIIIIIffiIIIIIIIffiII I l IT I I l I I I ITI I I I I l I l ITIIIIlIIIITIIIIIIIIITIIIIIIIITIIIIIIIInuIIIIIIfiIIIIIIIMIIIIIIIIHIIIIIIIMIIIIIIWII|IIIIIfiIIIIIIIIfiIIIIIIIIfiIIIIIIIIfiII l IT I I l I I I I I ITI I I II I IIITIIIIIIIITIIIIIIIIITIIIIIII|ITIIIIIIIIHIIIIIIIIMIIIIIIIflIIIIIIIIflTIIIIIIIW|I[IlI|lTllilllllmlllllllmllllllli I INVEZVTOR EZaIo 015 70370 BY & %zIs A TTORNE Ys Patented June 28,1938

PATENT OFFICE ELECTRODE Y Brian O'Brien, Rochester, N. Y. ApplicationApril is, 1934, Serial No. 121,221

I 2 Claims. 'This invention relates to electrodes for use with electriccurrentsto produce either arcsvor intermittent sparks.

An object of the invention is the provision of an improved electrodewhich will produce an are or spark particularly valuable and suitablefor the production of predetermined effects on a living body or onnon-living systems, such as milk or other foods.

Another object of the invention is the provision of such an electrodewhich will form a source of light of relatively high intensity in theultra-violet region of the spectrum, in the wave length range of 2750 Ato 3100 A, and which will have relatively low. intensity in wave lengthsbe-' low about 2700 A.

A further object is the provision ofan improved electrode especiallysuitable for use in treating food or the human skin to impart desirablecharacteristics thereto without injuring or changing the taste of orimparting other undesirable characteristics to the treated food, andwithout irritating the human skin.

To these and other ends the invention resides in certain improvementsand combinations of parts, all as will be hereinafter-more fullydescribed, the novel features being pointed out in the claims at the endof the specification.

In the drawings:

Fig. 1 is a diagram illustrating the spectral energy distribution of anare formed with an electrode constructed in accordance with the Ipreferred embodiment of the present invention, the'intensity of emissionbeing shown with relation to wave length expressed in Angstrom units;

Fig. 2 is a diagram similar to Fig. 1, but plotted on'a semi-logarithmicscale in which the ordinates represent logarithms to the base III ofintensity, while the abscissas represent, as before, wave length inAngstrom units;

Fig. 3 is a spectrogram of an arc formedby an electrode of carbonwithwhich is incorporated,

magnesium, vanadium, and chromium;

Fig. 4 is a similar spectrogram of anelectrode of plain carbon with itsordinary commercial impurities;

Fig. 5 is a similar spectrogram of an electrode composed of such carbonplus magnesium;

Fig. 6 is a similar-spectrogram'of an electrode of carbon plus vanadium;

Fig. 7 is a similar spectrogram of carbon plus chromium; v v v Fig. 8 isa similar spectrogram of carbon plus manganese Fig. 9 is a similarspectrogram of carbon plus arsenic;

Fig. 10 is a similar spectrogram of carbon plus zirconium;

Fig. 11 is a similar spectrogram of carbon plus 5 thorium; and

emissions of relativelyhigh intensity in the 15 ultra-violet region ofthe spectrum, in the wave length range of about 2750 angstrom units toabout 3100 A, and at the same time to avoid the highly destructive orirritating action of wave lengths below about 2700 A or 2750 A. Whilesuch shorter wave lengths may be removed by the use of light filters,yet the use of filters is frequently inefilcient and troublesome, sothat his preferredto employ a light source in which the emissions atwave lengths below about 2700 A are of relatively lowintensity.

According to the present invention, it is possi ble to produce a'highintensity of radiation in the desirable region from 2750 Ato 3100 A bythe use of an arc in which the electrode is made of or has-incorporatedin it (by coring or otherwise) the metal magnesium or compounds ofmagnesium, together with one or more other elements emitting spectrumlines which at least partially fill inthe gaps between the brighterlines of the magnesium spectrum lying in the wave length range of 2750 Ato 3100 A, and which added element or elements at the same time donotseriously increase the intensity of radiation at wave lengths shorterthan about 2700 A or 2750 A.

40 Within the above mentioned desirable range of 2750 A te 3100 A, thereare severalv important lines in the magnesium spectrum. In the case ofthearc spectrum, the more intense lines of -magnesium in this region areat wave lengths 2796 A, 2803 A, 2852 A, 3091 A, 3093 A, and 3097 A. Inaddition, there are a number of other ma nesiumlines ofmoderate.intensity within this spectrum range, but the lines specifically listedabove greatly exceed in intensity the rest of the 5 a magnesium lines inthe above spectral range, so

that there are important gaps left in the spectrum between these linesof relatively great iiitensity, which it is desirable to fill.

In the case of a spark between-electrodes containing magnesium or itscompounds, the same lines above mentioned appear, but in greatly reducedintensity, except the lines at 2796 A and 2803 A, both of which are ofmuch greater relative intensity in the case of the spark than in thearc. In the spark the lines at 2791 A, 2798 A, 2929 A, 2937 A, and 3105A become of appreciable intensity in addition to the intense lines at2796 A and 2803 A above mentioned, but there still remain substantialgaps between these lines.

A number of elements have been found with spectral emissions which tendto fill these gaps without seriously increasing the intensity ofemission at wave lengths less than about 2700 A or 2750 A. Such elementsare vanadium, chromium, manganese, arsenic, zirconium, thorium anduranium. These elements just named, together with magnesium, may beconsidered as a class, group or genus, the classification being based ontheir physical property of producing spectral emission of relativelyhigh intensity in the wave length range of about 2750 A to 3100 A,without producing intense emissions at wave lengths below about 2700 A.Furthermore, the elements magnesium, vanadium, chromium, manganese, andarsenic may be considered as a sub-group of the main group abovementioned, since the elements forming this sub-group are found inpractice to give comparatively greater intensity of spectral emission inthe above mentioned desirable range without corresponding undesirableshort wave emission. The remaining elements zirconium, thorium anduranium of the main group are less desirable in this respect.

, Vanadium and chromium are particularly suitable for use according tothe present invention,

and either or both of them may be used without magnesium, with orwithout one or mre of the other elements of the main group or genusabove mentioned, in special cases where it is desirable to excludemagnesium. Ordinarily, however, it is 7 preferred to employ magnesiumtogether with one or more of the other elements of the group.

For direct current arcs, and for sparking ap'- paratus (that is,apparatus to produce intermittent sparks) for use with either directcurrent or alternating current, the electrode may be-made entirely orsubstantially entirely of elements of the above mentioned maingroupfltogether with any necessary binder. For use with alternatingcurrent arcs, however, it is preferred to include a substantial quantityof carbon in the electrode,

and conveniently the electrode may be in the form of a tubular body ofcarbon with a core of ma terial including two or more of the elements ofthe above mentioned group.

A particularly satisfactory electrode, which forms the preferredembodiment ofthe invention 7 under many circumstances, is one in whichmagnesium, vanadium, and chromium are all employed. These materials giveexcellent results when used in the proportions of 100 parts ofmagnesium, 20 parts of vanadium, and 3 parts of chromium, mixed ifdesired with a quantity of soft carbon such as soft lamp black and witha suitable binder such as gum tragacanth, sodium silicate solution, orboth. Such a mixture can be used either as .the core for a carbonelectrode (or otherwise combined with the carbon) or as a completenon-carbonaceous electrode. When used with carbon, the non-carbonaceousmate,- rials should ordinarily constitue from three per centum to twentyper centum of the entire electrode, the optimum being approximately tenper centumin most cases. A cored carbon electrode,

are formed by a cored carbon electrode of the above mentioned preferredcomposition. In Fig; 2, the same emissions are plotted on a scale inwhich the ordinates, instead of representing the intensities themselves,represent logarithms to the base II) of the intensities, with theadvantage that relative intensities of emissions (as distinguished fromabsolute intensities) are correctly represented irrespective of wherethe zero point of the logarithmic scale be placed or whether itslocation be changed, and with the further ad vantage that thislogarithmic graph can be compared more easily with the spectrogramreproductions in Figs. 3 to 12, since these spectrograms are also on alogarithmic scale of intensities. From these two diagrams, it can bereadily seen that the intensity of emissions in the range of about 2750A to 3100 A is materially greater than the intensity below about 2700 A.

A reproduction of an actual spectrogram of an arc formed by an electrodeof this preferred form is illustrated in Fig. 3 of the drawings, thehorizontal scale reading directly in hundreds of angstrom units. It willbe seen from this spectrogram that such an are also has relatively highemission at wave lengths above about 3100 A, but such wave lengths aboveabout 3100 A may be disregarded because, so far as known at present,emissions in these upper wave lengths are neither beneficial nordetrimental.

The spectrograms of Figs. 3 to 12, inclusive, are special spectrogramsmade with a quartz spectrograph equipped with a rotating logarithmicspiral aperture sector disk and a projected intensity scale, and theheight of each vertical line of the spectrogram is in proportion to thelogarithm of the photographic intensity of emission at that wave length.a

While the above mentioned elements and proportions are preferred, it isto be understood that both the proportions and the elements em-v ployedin the electrode can be considerably varied wave length range from 2750A to 3100 A, but

these elements also produce more or less emissions in wave length below2700 A and this must be taken into account when selecting the elementsto be used and determining the proportions in which they are to be used.

Fig. 4 is a spectrogram, of the same special type shown in Fig. 3,showing emissions from an electrode of plain carbon in its ordinarycommercial form with commercial impurities. Fig. 5

is a similar spectrogram of such an electrode to l which magnesium hasbeen added, and Figs. 6 to 12, inclusive, are similar spectrograms ofcarbon electrodes to which have been added, re-

spectively vanadium, chromium, manganese, ar-

. senic, zirconium, thorium, and uranium. [Thus these spectrograms ofFigs. to 12, inclusive, show the characteristics of each of the elementsof the main group or class above mentioned,

' and, with this information at hand, those skilled in the art canreadily combine the various desired elements in proper proportions toproduce the desirable result of high intensity of emission in the rangeof about 2750 A to 3100 A,, and relatively low intensity of emissionbelow. about 2700 A. As willbe seen from the spectrograms, magnesium,vanadium, and chromium have the most desirable characteristics from thestandpoint of this invention, and the other elements of the class havedecreasingly desirable characteristics approximately in the order inwhich they have been named.

From the various characteristics of the-various elements of the group orclass, it is apparent that all of these elements could not be used inthe same proportions. For example, the propor-" tion of vanadium couldbe increased somewhat or reduced to about one quarter of the proportionindicated as the preferred construction,

' without undesirable effects, and the chromium could be reduced orincreased several fold in proportion to the other components withoutundesirable effects. But if manganese or arsenic were substituted forthe chromium or vanadium,

they would have to be used-generally in lesser.

amounts than the vanadium in order that appreciable emission at wavelengths less than 2700 A may be avoided. This is in part due to the.-influence which one element may exert upon the emission of energy byanother element si-v about 2750 A to 3100 A is tobe secured in propor Ition to the emission of wave lengths less than about 2700 A.

When speaking of the various elements which may be used in theelectrode, it is to be understood that the elements may be employedeither inithe metallic state or in the form ofany suit-' able compound.

As mentioned above, sodium silicate may be used as a binder for theother components of the electrode. While this material has certaindesirable characteristics, it is also found to have certaincharacteristics which are undesirable from the standpoint of the presentinvention, so that sodium silicate should be used as sparingly aspossible; Furthermore, it is seen from the explanation given below thatother materials are found to possess the same desirablev characteristicsas sodiumsilicate without having its undesirable characteristics, andsuch other materials may be used, according to the present invention, toreplace sodium silicate wholly or in part.

- It has been known for some time that sodium and potassium silicateshave a'beneflcial effect in causing alternating current arcs and othercarbon arcs to burn more smoothly, and for this reason,vthese silicateshave been called "arc sus-e taining materials, but the reason for thisaction does not appear to have been understood. This -arc sustainingeizect of sodium and potassium silicates is a desi able characteristicfrom the standpoint of the present invention.

But an important undesirable characteristic, from the standpoint of thepresent invention, is that the spectral emissions of silicon are highlyobjectionable if present in any appreciable amount, for silicon emitsconsiderable intensity in the neighborhood of wave length 2500 A.

It is now found that it is not the silicon in sodium silicate orpotassium silicate that gives these materials, their are sustaining,character, but rather the alkali therein which produces this result.Sodium and the other alkalies have a relatively low ionizationpotential. Because of this low ionization potential, the Saha thermalionization as well as the ionization due to bombardment in the arcstream is high. Moreover, at and near the zero point of the current wavein an alternating current arc, a considerable number of the alkali atomsin the arc stream re main ionized,-and thus they may greatly aid the arcin reestablishing itself as the alternatingcurrent reverses in directionfrom the previous half cycle. In addition to alow ionization potential,the alkalis and some of theircompounds have a low thermionic orRichardson work function. Thus in those cases where their boiling pointsare suiiiciently high so that they or their compounds 'cover'part of theactive electrode surface, their high thermionic emission also assists inthe reestablishment of the arc when the current re-' verses. This latterproperty is possessed also by many metals other than the alkalis,including, for

example, vanadium and chromium..

Thus it followsthat from the electrical arc sustaining standpoint, it isthe presence of alkalies rather than of silicon, that is desirable asassisting in proper functioning of the arc., But from'an opticalstandpoint the presence of two much alkali tends to suppress thespectrum lines of other elements, becausev the alkali ions carry anunduly large proportion of the current in the are stream, thus reducingthe ionization of other elements. In this way, some of the emissionlines of carbon itself and of carbon compounds may also be partiallysuppressed. In some cases, this suppression is desirable as, forexample, sodium or potassium may be useful in partially suppressing thesilicon lines in the neighborhood of wave length 2500 A, but unlesscaution is exercised, some of the desirable spectrum lines of otherelements may also be partially suppressed. It should also be pointed outthat, in contrast with the suppressing characteristics of alkalls in the1 arc stream, high thermionic emission does not, in general, ap reciablyenact the spectrum energies either of 'e elements causing the thermionicemission or of other elements which may be pres- This isbecausethermionic emission is from solid or liquid substances on the electrodesand v not in'the'arc stream, andhence from atoms which are not, at thattime, emitting spectrum lines. thermionic emission is not detrimentalfrom an optical standpoint, although the use of a readily ing tosuppress some of the desirable lines. of

.spectral emission. Moreover, it is found that when alkali is added inincreasing quantities, the arc sustaining" properties appear'beforethere is enough alkali present to cause any serious suppression ofdesirable wave. lengths from other ele- Thus the use of an electrodehaving high ionizable vapor substance in the are stream it- I self maybe detrimental as suppressing or tendments. Hence a relatively smallquantity of alkali is not particularly harmful from the opticalstandpoint, but is beneficial from the electrical arc sustainingstandpoint, and can be used to advantage.

From the above explanation it is seen that silicon is undesirable forthe purposes of the present invention and should be used sparingly if atall; and that the desirable arc sustaining properties may be secured byusing alkalis (preferably in relatively small amounts, to avoidundesirable suppression characteristics) or other materials having highthermionic emission. Alkali compounds such as the carbonates are useful,as they aid in sustaining the arc while avoiding the undesirablecharacteristics of the silicates.

. Instead of an alkali metal, an alkaline earth such as magnesium may beused as an aid in sustaining the are. But in the case of an alkalineearth, a much' larger quantity is usually necessary, to produce the sameresult, than in the case of an alkali metal. The addition of a largeamount is not objectionable in the case of magnesium, however, becausemagnesium is one of materials of the group or class already named ashaving desirable spectral characteristics for the purposes of thisinvention.

The alkaline earths are also valuable because their oxides (such asmagnesium oxide, whichforms rapidly under working conditions whenevermagnesium is present) have high boiling emission; and that when usingsuch other alkaline materials, they should (with the exception ofmagnesium and its compounds) be used in small quantities, so as toprovide the desirable arc sustaining characteristics without producingserious of these materials not only are in the class or group ofelements having the, desired spectral emissions, but also are materialshaving desirable arc sustaining characteristics.

An electrode made in the preferred form above disclosed gives a goodlight which closely simulates the appearance of natural sunshine, andwhich is cheerful for sick patients. It is also of commercial value inthe irradiation of various products, such as' milk, and the color valueof the light is such that it enhances the appearance of the productsbeing irradiated. For example, milk undergoing irradiation from suchlight has its natural rich and-creamy appearance fully maintained oreven heightened, in contrast to the bluish or skimmed-milk appearancegiven even to rich creamy milk during irradiation by certain other formsof lights.

I claim:

1. A carbon electrode having a core made of a mixture consistingsubstantially of magnesium, vanadium, and chromium, in which there areat least five parts of vanadium to each part of chromium, and at leastfive parts of magnesium to each part of vanadium.

2. A carbon electrode having a core made of a mixture consistingsubstantially of magnesium, vanadium, and chromium, in the proportionsof approximately one hundred parts of magnesium, twenty parts ofvanadium, and three parts of chromium.

BRIAN OBRIEN.

